In the past several decades, automotive manufacturers have made great strides in enhancing the safety of motor vehicles in terms of impact protection. While seat belt systems provide a high degree of occupant impact protection, deployable impact protection devices such as inflatable air bags are now in common place use in motor vehicles. Air bags for the driver and passenger side front seat occupants are commonly found in vehicles today. Until recently, the primary attention in the design of deployable restraints was directed toward providing frontal impact protection.
Motor vehicle manufacturers and their suppliers of safety systems are increasingly focusing on deployable devices providing side impact protection. Statistically, side impacts pose a greater probability of causing significant occupant injury as compared with frontal impacts. This difference is largely due to the limited energy absorption structure available in side impact situations, especially for the "on side" occupant. In response to this concern, vehicle manufacturers and suppliers are developing side impact air bags which are mounted either to the door or body pillar structure, or to the seat back of the occupant seat. In response to a signal from a crash sensor, an inflator generates gas. The expanding gas fills a woven fabric air bag which fills an area between the door and occupant. To date, the primary emphasis for deployable side impact devices has been protecting the torso and pelvic area of the occupant. Providing head protection for side impact collisions poses a number of design challenges beyond that posed for torso and pelvic protection. In the case of a side impact air bag for torso and pelvic protection, the door structure acts as a "reaction plate" to support the air bag as it is compressed by the occupant thus providing energy absorption. In the head area, a convenient reaction plate surface is not present. This is the case since the side door window is movable and thus can be in the down position during impact and is made of a brittle material. Accordingly, the window cannot be relied upon as a reaction plate for an air bag. One approach toward resolving the above referenced difficulties for side impact head protection is to provide a deployable fabric shade or curtain tied to the door frame which provides an instantaneous support structure for an air bag or deployable safety curtain. After detection of the side impact crash, the system pulls down a curtain which covers the upper portion of the side window door. In one design of such device, the deployment mechanism incorporates a pyrotechnically powered actuator coupled to a wire and pulley system to pull down the curtain from its non-deployed stored state into a deployed condition. Although such a system appears workable, it is believed to be difficult to incorporate it into a vehicle structure.
In motor vehicle design today, size and mass constraints are of critical importance. This is especially true for the side frame area of an automobile body where there is very tight packaging space. In order to be cost effective, the design of a deployable side impact restraint device should be applicable across many vehicle platforms and provide low cost fabrication and assembly, with high quality and reliability.
Thus, there is a need for a side impact head restraint which can provide a low cost means of deploying head protection in side impact collisions. There is also a need for a deployment means which works without substantial accommodation or redesign by the vehicle. Furthermore, there is a need for a side impact head restraint system which meets the minimal packing space requirements for installation in the side frame area of an automobile door.